Paper and method of making



y 1935- J. L. M CLELLAN 2,008,142

PAPER AND METHOD. OF MAKING Filed May is, 1932 hum/70,2

I L/W/IIZ Wf/ ,4/1 wwwm mercerization of the fiber. Consequently, suchpreheated solution of sodium hydroxide of 17 Patented- July 16, 1935 QUNITED STATES PATENT OFFICE 2,008,142 PAPER AND METHOD OF MAKING JamesL. llTClellan, Littleton, Mass., 'assignor to Hollingsworth & VoseCompany, Boston, Mass a corporation of Massachusetts 1 Application May16, 1932, Serial No. 611,573

12 Claims. (CI. 92-13) This invention relates to a method for thepreptreatment does not amount to more than a puriaration of paper pulpand for the production of flcation treatment of the cellulose fibers. aporous, open fibrous sheet of paper therefrom. It is an object of thepresent invention to pro,-

It has heretofore been proposed in the art to vide a more convenient andalso a more reliable 5 treat a sheet of paper or porous web composedprocess for the preparation of fibrous pulp, in 5 l of wood pulp, kraft,sulfate, or like cellulose which the fibers are mercerized'but may ormay fibrous materials generally by immersing the not be curled, ashereinafter described, and which sheet in a caustic soda solution havinga concenmay be made into a porous sheet of open formatration of 20% to25% sodium hydroxide for 9, tion. The fibers or fibrous material may bedevery brief interval, followed by drying and washrived from wood fiberpulp, such as kraft pulp,

ing the dried sheet with a. neutralizing bath of manila rope, or cottonfibers, or from mixtures sulfuric acid. Such treatment is effective toswell of such fibers. It is also an object to provide the fibers of thesheet, and the final product is a treated fibrous material in the formof a puriporous and of open texture somewhat resembling fied pulp whichmay be subsequently made into 5 felt. Such procedure is, however,diflicult in paper of the desired properties having an open practice andtends to disrupt the sheet owing to porous structure which renders itnot only soft the necessity of excessive handling when wet. but readilyand completely absorptive of impreg- Moreover, it also presents greatdifilculty by any hating materials, which may be of comparativelyreasonably practical treatment in obtaining a high viscosity such asrubber latex. Other obsufficiently washed sheet to be free of thecaustic jects will appear from the following disclosure. 20 soda orsulfuric acid used. In the event that The process of the presentinvention includes any of these reagents is left in the sheet, it thepreliminary preparation of the sulfate, cottends to disintegrate anddestroy the final prodton, or true hemp (such as manila) fibers, eithernot during storage and subsequent use. in the form of a pulp or in theform of laps, in

It has also been proposed to treat a preformed accordance with the usualprocedures. The fiber 25 porous sheet of paper, containing a mixture ofas thus obtained is immersed and dispersed in a cotton linters or othercellulose fibers which have caustic treating solution of mercerizingstrength been given a preliminary caustic cook, with simi- (preferablypreviously heated to a temperature lar uncooked fibers such ascottonlinters, kraft, somewhat short of the boiling point) whichconjute, etc. The treatment is said to be conducted tains sodiumhydroxide in a concentration of ap- 30 with a caustic solutiondefinitely controlled as to proximately 12% to 15%, as represented by aconcentration and temperature within the limits Baum value of 15 to 20Baum. The ratio of of 1% to 10% sodium hydroxide (in the initialsolution to fiber may be varied, but is preferably treatment of thecooked linters), and between relatively low, andthe fibers arepreferably uni- 8% and 18% sodium hydroxide in the final treatformlydispersed throughout the solution. The 35 ment of the paper sheet madetherefrom, at. a mixture is then agitated without further heatingtemperature between 0 and 104 C. The fibers for several hours, whereuponthe charge (espein t resulting product are said to be curled and ciallywhen the proportion of solution is low) aspuff d o as to pr du a higy'porous paper sumes adry, crumbly condition somewhat resem- 40 sheet orweb. Such pr edure s, however. subbling corn meal. It is then dumped andwashed 4e J'e t the S difiieulties as the foregoing D 'O completely freeof reagents and may be diluted ess with respect to a dl a so to e Sa ewith water to any concentration desired and run liability of retainingdeleterious reagents in the i t th form of h t on a paper machine in fid product in Spite of Continued Washingcordance with the usual practiceof the art.

It has further been proposed to tr paper A specific instance of thepractical applica- 45 Scrap With a caustic Soda Solution of Beum tion ofthe invention will be described with ref- (app y 5 NaOH? followed y Waerence to the accompanying drawing, in which: s and making n a sheetuofp p r r paste- Fig. 1 is a diagrammatic side elevation of the boardwhich is coated on one side and shellaced apparatus employed inpreparing the pulp; and

on the other for the manufacture of stereotype Fig. 2 is a similar viewof the paper making 50 matrices and the like. But it will be observedmachinery. that in such procedures the concentration of the Referring tothe drawing, the pulp, which may sodium hydroxide treating solution isrelatively be the usual sulfate or kraft pulp, is chargedlow,-appreciably below that necessary to efiect in the rotary boiler l,which already contains a Baum, for example, heated to a temperature of180 F. The ratio of pulp to caustic solution may be such as to provide 1to 2 pounds of sodium hydroxide for each pound of' pulp. The drum isthen closed and rotated for a period of 4 to 5 hours, the temperaturebeing allowed to drop as a natural result of loss of heat to thesurrounding atmosphere.

The treated charge is then dumped into the stock box 2 by inverting theboiler and opening the manhole 3. At this stage the charge is apparentlyfree from excess of solution, and, as above suggested, resembles in itsconsistency a batch of wet corn meal. It is next dumped into the beatingengine 4 into which fresh water is introduced through decline 5 and thereagent solution separated from the pulp by withdrawal through therotating washer or screen 5. The washed pulp is then transferred to thestuff chest 7 in which it is agitated and diluted to a sumcient fluidityto be withdrawn by the pump 8 and delivered to the regulating tank 9where its consistency may be further checked and controlled by theaddition of water by the inlet pipe ii if necessary. The pulp is thenpassed to the Jordan 52 and thence into the stuff chest i3 which isprovided with an agitator (not shown) to make and keep the pulp uniform.

The pulp as thus prepared may be delivered to the head box 14 (Fig. 2)where it is diluted with additional quantities of water from the inletpipe l5 and thence is run into vat i6. From here it is taken up oncylinder H, in the usual way, in the form of a sheet which istransferred to the wet felt iii.

The sheet of paper thus formed is carried by the wet felt, supported byrolls 2 i, 22, 23 over suction roll 25, and thence to a carrying felt 25supported by rolls 26 which convey the sheet to a series of drier rolls21, 28, supported by conveyor belt 29 and thence to calender stack 3|,if de-' sired, from which the sheet is drawn bytake-up roll 32.

In accordance with this procedure, the pulp is not only given anintimate and definitely controllable mercerizing treatment with respectto its individual fibers, but is also completely free from reactionby-products and from excess of the reagent materials used, before it isformed into a paper sheet. It accordingly does not tend to retain thereagent materials used, as a sheet of paper does, and hence provides apurer fibrous product. The pulp as thus treated is, moreover, found tobe entirely suitable for sheeting out into paper in the usual way and toproduce a finished sheet which is not only characterized by the desiredcurly, wool-like structure of the individual fibers but also by a veryporous open felt-like sheet structure. This renders it especiallysuitable for purposes in which. such papers are required to besubsequently impregnated, as by rubber solutions, latex, or the like.

The present treatment is characterized by being applied to the fibrousmaterial in dispersed permits them to curl freely under the action ofthe caustic. The initial, relatively high temperature of the reagentsolution assures complete wetting, admixture, and reaction by thecaustic upon the mass of fibers, while the subsequent cooling checkssuch reaction gradually, thus preventing material. weakening anddisintegration of the fiber substance. The final and rapid washing outof the reagent still further checks and overcomes continued action,thebrief time interval and low temperature of the same preventing appreciable swelling of the fibers which would otherwise occur. At the sametime the introduction of other reagents such as sulfuric acid isavoided, and when the caustic has been washed out, the fiber pulp issubstantially clean and in open,

curly condition and not of a gelatinous condition or individuallyswelled. At the same time, the treated fibers are competent to form apaper sheet according to the usual paper making practices which is open,free, relatively strong, free from impurities, and admirably adapted forsuch operations as require an open, easily penetrated structure, as forimpregnation, absorption, and like functions.

It may be especially noted that the kraft or cotton fibers in the abovetreatment'are mercerized and also rendered curly thereby. With manilarope fibers, however, and the other true hemp fibers, (i, e. excludingcommon hemp) it is found that the fibers are not curled by the treatmentbut remain as substantially straight, rod-like fibers. Both types oftreated fibers are, nevertheless, susceptible of being felted into aporous, open sheet, and are especially to be desired for the purpose ofsubsequent impregnation.. In such cases where the impregnated fibrousmaterial is to be thereby bonded together, the inherently high fiberstrength of the manila hemp is rendered effective, and the finishedsheet is exceptionally strong and otherwise constitutes an especiallyvaluable commercial product. Likewise, the kraft or cotton pulp(particularly when long-fibered) which forms an open, porous fibroussheet, may be readily impregnated with fluids and the like. .When suchimpregnation also serves to bond the fibers together, they constitute atough sheet in which the initial fiber strength, though lower than-thatof manila or hemp fibers, is relatively high and is supplemented by thecurly, entangled relationship of the fiber components.

I claim:

1. Method of preparing paper pulp, containing cotton, hemp, kraft orsulfate fibers, comprising the steps of mixing the same with a causticsolution of mercerizing concentration at a temperature of approximatelyF., agitating the mixture while causing the temperature of the same todrop gradually, and washing the fiber substantially free from solublereagents and byproducts.

2. Method of preparing paper pulp, containing true hemp fibers,comprising the steps of mixing the same with a caustic solution ofmercerizing concentration at a temperature of aping the same with acaustic solution of mercer-.

izing concentration at a temperature of approximately 180 F., agitatingthe mixture while cansing the temperature of the same to drop gradually, and washing the fiber substantially free from soluble reagentsand lay-products.

4. Method of preparing paper pulp, including cotton, hemp, krait orsulfate fibers, comprising "the steps of mixing the same with a causticsolution of mercerizing concentration at a temperature of approximately180 F., agitating the mixture while causing the temperature of the sameto drop gradually, washing the fiber substantially free from solublereagents and byproducts, and thereafter diluting the pulp and runningthe same into theiorm of paper sheets.

5. Method of preparing paper pulp, including true hemp fibers,comprising the steps of mixing the'same with a caustic solution ofmercerizing concentration at a temperature of approximately 180 F.,agitating the mixture while causing the temperature or the same to dropgradually, washing the fiber substantially free from soluble reagentsand by-products, and thereafter diluting the pulp and running the sameinto the form of paper sheets.

6. Method of preparing paper pulp, including manila fibers, comprisingthe steps of mixing the same with a caustic solution or mercerizingconcentration at a temperature of approximately 180 F., agitating themixture while causing-the temperature of the -same to drop gradually,

washing the fiber substantially free from soluble reagents andby-product's; and thereafter diluting the pulp and running the same into.the'

form of paper sheets.

'7. Method of prepari'ng'paper pulp, including after-diluting the pulpand running the same into the iormot paper sheets.

8;.-Method of preparing paper pulp, including cotton, hemp -kratt orsulfate fibers, comprising the steps of mixing the same with a causticsolution 01 mercerizing concentratiombetween 12% and 15% NaOH at atemperature of approxia mately 180 F., agitating the mixture whilecausing the temperature of the same to drop gradually, washing the flbersubstantially free from soluble reagents and by-products, and thereafterdiluting the pulp and running the same into 10. Method of preparingpaper pulp, includ ing cotton, hemp, krait or sulfate fibers, comprisingthe steps of mixing the same with a caustic solution of mercerizingconcentration at a temperature of approximately 180 F., agitating themixture, cooling and washing the fiber substantially free from solublereagents and' by-products, diluting the pulp, and running the sameinto'the form of paper sheets.

11. Method of preparing paper pulp, includ-- ing cotton, hemp, kraft orsulfate fibers, comprising the steps oi' mixing the same with a sodiumhydroxide solution of mercerizingconcentration at a temperature ofapproximately 180 F., in approximately the proportions of two pounds ofdry pulp to one to two pounds of sodium hydroxide, while causing thetemperature of the sametodrop gradually, and washing the fiber,substantially free from soluble reagents and by-products.

12. Method of preparing paper pulp, including cotton, hemp, knit orsulfate fibers, comprising the' steps of mixing the same with a sodiumhydroxide solution of mercerizing concentration at a temperature ofapproximately F in thefapproximate proportions of two 7 pounds of drypulp to one to two-pounds of sodium hydroxide, while causing thetemperature oithe same to drop gradually, washing the i'lbersubstantially free from'soluble reagents and lay-products, and dilutingthe pulp and running the same into the form of a paper sheet.

i JAMES L. McCLELLAN.

